Rod and bar mill

ABSTRACT

A rod or bar mill stand intended as the first stand of a continuous rod or bar mill has work rolls carried by rocking mountings which are driven to cause each roll to follow an elliptical path. In each cycle of operation, the work rolls thus roll over and reduce the work before losing contact with the work and returning to their starting positions. The work rolls are additionally driven about their own axes at a peripheral speed so chosen that the work is urged in the feed direction.

United States Patent Wilson Sept. 30, 1975 [54-1 ROD AND BAR MILL 3.103.139 9/1963 Suxl 72/190 3.690.138 9 1972 WVh 72 I89 [75] Inventor: Alexander lan Wilson, Sheffield. v k u England i I l73] Assignee: Hille Engineering Company Limited. 'l') ""P f l shcfficld, England Attorney. Agent; or FlrmBrlsebois a Kruger [22] Filed: May 20, 1974 v [21] Appl. No.: 471,832 57 7 ABSTRACT [30] Foreign Application Priori. Data A rod or bar mill stand intended as the first stand of a M I8 197.; U d K d 5x699? continuous rod or bar mill has work rolls carried by i m rocking mountings which are driven to cause each roll to follow an elliptical path. In each cycle of operation, 7 v

13:;12123 the work rolls thus roll over and reduce the work bei 406 407 fore losing contact with the work and returning to le 0 ea 1, their starting positions. The work rolls are additionally driven about their own axes at a peripheral speed so y References Cited chosen that the work is urged in the feed direction.

UNITED STATES PATENTS v I 17 Claims, ll Drawing Figures 3.049.948 8/1962 Sendzimir .l 7Z/l90 v I l US. Patent Sept. 30,1975 Sheet 1 of 4 3,908,423

US. Patent Sept. 30,1975 Sheet 2 of4 3,908,423

% US. Patent Sept. 30,1975 Sheet3 0f4 3,908,423

F/QSA, FIGSB. FIGSC. F/QSZJ.

U.S. Patent Sept. 30,1975 Sheet4 of4 3,908,423

ROD AND BAR MILL The present invention relates to rod and bar mills and is particularly concerned with continuous multi-stand mills for rolling rod and bar from billets, which are introduced into the stand at high temperature.

There is a continuous requirement to produce rod in larger and larger coil weights; in other words, there is a demand to increase the amount of rod rolled from a single billet. That objectivee can be achieved by increasing the length of the billet, or by increasing the cross-sectional area of the billet. The first expedient necessitates the provision of longer furnaces and corresponding increases in capital cost.

The other expedient of increasing the cross-sectional area of the billet is also faced with difficultics, The ratio of the speed at which the work enters the first stand of the rod mill train to the speed at which the final rod leaves the last stand is directly proportional to the overall reduction effected in the mill. Therefore, for a given cross-sectional area of the final rod, an increase in the cross-sectional area of the billet can be accommodated only by increasing the speed at which the rod leaves the final stand, or by decreasing the speed at which the billet enters the first stand. Much work has been done in A designing finishing rod mill stands to operate at higher and higher speeds, and a limit has been reached with present designs. Similarly, the speed of operation of the first, or roughing, stand has been progressively reduced and a limit of approximately 0.08 m/sec. has been achieved for the entry speed into the first stand; below that figure, there is a very real danger of fire cracking of the rolls occurring.

The high speed of delivery of rod from the final stand under modern practice is also accompanied with further problems. Special expedients must be adopted to coil rod at high speed and this, in turn, involves expensive and sophisticated equipment.

Thus, efforts have been directed, so far without success, towards a first stand capable of rolling billets at extremely low work speeds. The achievement of such low speeds would enable greater coil weights to be rolled, if the present high speeds from the last stand are tolerated, by increasing the cross-sectional area of the billets. Alternatively, low speed rolling in the first when the rolls are in contact with the work, only be engagement with the work. Consequently, the mill stand is capable of effecting a high reduction, only if the work is caused to move through the stand at a relatively high speed, well in excess of the speed of 0.08 m/sec referred to above: the fact that the rolls are rotated about their own axes solely by contact with the work has the result that all forward movement of the work must be accomplished by the downstream pinch rolls which must additionally restrain the work against the substantial rearwardly directed reaction forces applied to the work by the work rolls. The pinch rolls must therefore apply a considerable pressure on the work to an extent that they themselves perform a reduction. The high pressure applied by the pinch rolls to the work is not necessarily detrimental where the work is moving at a high speed and on strip material, but would be impractical for low speed rolling, because of the fire cracking of the pinch rolls that would occur, as explained above.

The arrangement of the British patent specification cannot therefore be applied to solve the problem that exists in rod and bar rolling and that has been previously explained. The mill stand of that specification has the further disadvantage that, if it were used for rod or bar rolling at a high speed, multi-stand operation would be difficult, because the absence of forward driving of the work by the work rolls, due to those rolls being stand, without increase in the cross-sectional area of I the billet, enables a lower exit speed from the final stand to be achieved, with a reduction in the complexity of the coiler and other delivery equipment.

British patent specification No. 871997 describes equipment for reducing in a single pass the thickness of metals in slab, plate or strip form, the metal being fed by feed rollers through a heating chamber to a rolling mill stand, where a large reduction takes place, and thence by pinch rolls to a strip coiler. The rolling mill stand has a pair of work rolls, each of which is carried by a separate compound pendulum so arranged and freely rotatable, results in there being no synchronisation of the strands by the stand itself; a result it would be necessary to provide external means to synchronise the strands, those means having sufficient power to withstand the rearward forces applied to the strands by the stand.

The invention resides in a rod or bar mill stand for giving a primary reduction to a workpiece, comprising a housing, a pair of mountings swingingly supported by the housing on opposite sides of the pass-line, a work roll carried by each mounting and designed to effect a first reduction of the workpiece to a rod or bar, means for driving the mountings in synchronisation, the arrangement being such that the work roll axes are constrained to move in closed paths which, over a limited part approach the pass-line so that, in use, the rolls intermittently and simultaneously engage the workpiece on opposite sides, and means for driving each work roll about its axis. The means for driving the work rolls about their own axes are so arranged that the resulting peripheral speed of the rolls differs from the peripheral speed of the roll surfaces due to the driving means for the mountings to an extent that the workpiece is urged by the work rolls in the feed direction.

In other words, the drive means for the mountings and for the work rolls are so chosen that the roll surfaces in contact with the work have a net peripheral speed, of a direction and magnitude that the work is urged in the feed direction. Consequently, the mill stand is largely self-feeding, any feed means that may be provided being required to apply little traction to the work during rolling.

It follows that low work speeds, of for example less than 0.08 m/sec are possible, since, firstly, the work rolls, when in contact with the work, are turning at a peripheral speed which is high relative to the work feed speed and are therefore in no danger from fire cracking, and, secondly, the need for pinch rolls which apply a severe pressure on the work is eliminated and with it the danger of fire cracking of the. pinch rolls.

The self-feeding effect of the work rolls on the rolls has the further advantage that it enables multi-strand rolling to be performed, the strands being synchronised by the mill stand itself.

Each work roll mounting may additionally carry one or more back-up roll or rolls for the work roll, where there is a danger of the work roll bending unduly under the rolling load to which it is subject during contact with the work.

It is preferred to arrange that the work rolls engage and reduce the work when the work rolls are moving arcuately in the direction opposite to the movement of the work, since then skidding of the work rolls on the work is reduced. In that case, the peripheral speed of the work rolls due to their rotation about their own axis is in excess of the peripheral speed of work roll surfaces due to swinging movement of the mountings, in order to achieve the desired urging of the work in the feed direction.

The invention includes a continuous rod or bar mill having a train of rod or bar mill stands, of which at least the first stand is as set out above.

The invention further includes a method of continuous rod or bar rolling comprising passing a workpiece through a train of rod or bar mill stands, causing the axes of each work roll of at least the first stand of the train to follow a closed path so that the work rolls contact and reduce the workpiece over a part only of the paths, and driving the work rolls of that stand about their axes to give a peripheral speed differing from the peripheral speed of the roll surfaces due to the movement of the roll axes, so that the workpiece is urged in the feed direction. Preferably the mean linear speed of the workpiece is less than 0.08 m/sec.

The invention will be more readily understood by way of example, reference being made to the accompanying drawings, in which FIG. 1 is a side view of the stand,

FIG. 2 is an end view of the stand,

FIG. 3 illustrates an alternative form of gear box for the stand,

FIG. 4 shows the stand diagrammatically in relation to the furnace and the second stand,

FIGS. 5A, 5B, 5C, and 5D illustrate the operation of the arrangement, while FIG. 5E shows the elliptical path of a roll of the stand in relation to the work,

FIG. 6 shows a preferred modification of the mill stand of FIGS. 1 and 2, and

FIG. 7 illustrates the movements of the rolls of the stand of FIG. 6 in relation to the work.

The rod stand illustrated in FIGS. 1 and 2 of the drawings has a pair of spaced housings 12 mounted on a base 13 and carrying in bearing sleeves 14 two eccentric shafts I5, 16. Eccentric shaft 15 carries two rocking frames 17, 18, which are secured integrally together by a tie and which are forked to receive roll chocks 21. Above the eccentric shaft 15, the frames l7, l8 carry a rod 22 which is restrained to movement in the vertical plane by a pair of links 23 pivoted to the rod 22 and to the housings 12. The chocks 21 support the ends of a rod work roll 24, which is shown as having four grooves for multi-strand operation, but which may equally be constructed for single strand operation.

Below the pass-line, a similar work roll 25 is mounted by a mechanism similar to that described for roll 24, the various parts of the mechanism for supporting roll 25 being given similar reference numerals with the suffix A.

In FIG. 1, the direction of movement of the work, the direction of rotation of the rolls 24, 25 about their own axes, and the direction of swinging of the mounting frames during contact of the rolls with the work are indicated by the arrows A, B and C respectively.

Shafts 15, 16 and the rolls 24, 25 are driven, the gear box being shown at the right-hand side of FIG. 2. The input shaft 30 of the gear box has keyed to it a large gear wheel 31 meshing with a similar gear wheel 32 keyed to a shaft 33. Shaft 30 is coupled directly to eccentric shaft 16 through propeller shaft 34 and universal couplings 35. Similarly, shaft 33 is coupled to shaft 15 through propeller shaft 36 and couplings 37. Shaft 30 also carries a small gear wheel 38 in mesh with gear wheel 40, which is splined to a shaft 41. Shaft 41 drives roll 25 about its own axis through couplings 42 and a propeller shaft. In similar manner, a gear wheel 43 keyed to shaft 33 drives a gear wheel 44 on a further shaft 45, which in turn drives roll 24 about its axis through universal couplings 46 and a propeller shaft.

The operation of the stand is illustrated in FIG. 5, where the movements are much exaggerated. In the position shown in FIGS. 1 and 2, the frames 17, 18 and 17A, 18A lie in a common plate at right angles to the pass-line and the eccentric shafts 15, 16 are so disposed that the rolls 24, 25 are in the position at which their separation is smallest; this arrangement is shown in FIG. 5A, where the work to be reduced is illustrated as a billet 50. The shafts 15, 16 are rotated to cause the frames l7, l8 and 17A, 18A to swing away from the vertical in the direction contrary to the direction of movement of the work and are also moved progressively away from the pass-line until the position shown in FIG. 5B is reached. During that movement, the rolls 24, 25 are in contact with the work and are turned about their axes in the directions opposite to the directions of swinging of the frames so that the rolls 24, 25 roll over the work and thereby progressively reduce the billet. After a specified movement in contact with the billet, the rolls are withdrawn from the work, as shown in FIG. 5B. Thereafter, the rolls return from left to right above the work as shown in FIGS. 5C and 5D, before moving again from right to left to execute the next reduction of the work.

Due to the swinging of the mounting frames 17, 18 and 17A, 18A, the axes of the rolls 24, 25 cyclically execute closed paths, which approximate to ellipses, and the rolls 24, 25 are in contact with the work over a part only of those elliptical paths, the billet 50 being progressively reduced by the intermittent contact.

The amplitude of movement of the roll axes is sufficiently small to permit the rolls 24, 25 to be driven through the universal couplings 42, 46. The torque to be applied to the rolls is however only a fraction of that of normal rod mills, because of the intermittent contact with the work.

The gearing in the gear box is so chosen that, during the rolling part of the cycle of the swinging frames, ie between the positions shown in FIGS. 5A and 58, each roll 24, 25 is driven about its axis at a peripheral speed which is equal to the peripheral speed given to the surfaces of the roll in contact with the work by the swinging movement of their mounting frames, plus an additional component equal to the required forward speed of the work and the likely slipping of the rolls on the aides-1423 work. Tl'ie additional component of the roll speed enif suresthat the work 50 is urged forward in the feed direction. and applies a forward force to thework countering the rearward reaction forceapplied to the work by the reducing action of the stand. The mill stand is 4 thus largely self-feeding, any feed means for the work,

such as the pinch rolls shown in FIG: 4 or the downstream stands of the mill, being required to provide lit- .tle tractive effort and merely ensuringthat the work continues to move forwardly during the forward swing of the mounting frames (left to right in FIG, 5), when the rolls 24, 25 are out of contact withthe work.

,The rolls 24, 25 are thusdriven about their axes at peripheral speeds which are high compared with the feed speed of the work; the danger of fire cracking or other damage to the .rolls by the high temperature of the work 50 is largely eliminated.

Because the stand is self-feeding, multi-strand rolling is made possible, the various strands being fed forwardly. at equal lineartspeeds. External synchronisation means for the strands thus become unnecessary.

The rolls 24,25 are caused to rotate about their axes I .at a steady speed at all times, thus avoiding the need to speed up, or even start from rest during-each revolution of the eccentric shafts 15, 1 6. v

By increasing the rate of rotation of the eccentric shafts. 1 5, 16 relative to thespeed at which the billet is fed forwardly into the stand, the size of the portions of the billet rolled ateach eccentric revolution is reduced, and vice versa. Due to the flat-bottomed path described by the rolls, the degree of ripple on the billet is very small and the spacing of those ripples is dependent upon the ratio of the rotational speed of the eccentric shafts 15, 16 to the billet-speed. The idealamount to be rolled per eccentric revolution depends upon the particular application ,"too little resulting in working the material skin only and not giving sufficient penetration of the rolling pressure, which is however considerably less than the corresponding rolling pressure when the roll axes are stationary.

By means of the stand illustrated in FIGS. 1 and 2 of the drawings, it is possible to achieve a reduction in the one stand of approximately 50%. This in turn means that the speed of the second stand of the train maybe 0.08 m/sec., the recognised minimum speed for a conventional rod stand, and the final finishing speed of the train is half what it would otherwise have been. This in turnresults in tremendous economies because the need for finishing stands operating at high speeds no longer obtains and sophisticated and expensive equipment for 2, the r011 24, 25 are driven at a fixed speed relative to the eccentric movement of the rolls. In order to achieve greater flexibility, the rolls 24, 25 can be driven independently'of the eccentric shafts 15, 16, for example as shown in FIG. 3. The gear box of FIG. 3 has a second, independently driven, input shaft 60, which drives a lay shaft 61 through gear wheels 62, 63. Shaft 61 is coupled to roll 25 through universal couplings,

' one of which is shown in FIG; '3 at 42. Shaft 61 also drives a further shaft 64 through a pair of gear wheels 65 and shaft 64 is coupled to roll 24 through universal couplings, one of which is shown at 46.

Again, the rolls 24, 25 may have a torque or soft drive, as by using hydraulic couplings in the drive connections'to provide the whole or a part only of the rolling torque.

As explained earlier, the axis 'of each of the rolls 24, 25 (FIGS. 1 and 2) is caused to move cyclically along a closed path, which approximates to an ellipse. With .the configuration of FIGS. 1 and 2, the major axis of the ellipse'is'parallel to the pass-line, the work being rolled over an arc of the ellipse between the minor axis and the major axis i.e. between the points 70 and 71 in FIG. 5E which demonstrates the elliptical path 73 of the working surface of one of the rolls.

In'the preferred modification shown in FIG. 6, the links 23, 23A connecting the frames 17, 18 and 17A, 18A with the housings 13 are increased in length relative to .those, of FIG. 1 with the. consequence that, I

when the rolls 24, 25 have their closest separation as shown, the planes through the roll axes and the rods 22, 22A are inclined to the vertical. That has the effect of tiltingthe major axes of the ellipses 74, 75 round which the roll axesare caused to move so that they converge towards the pass-line in the direction of work feed, i.e.

- as indicatedin FIG. 7. The work is then rolled over longer paths 76-77 and 78-79 of less curvature than in the case of FIG. 5E. Two advantages result; firstly. the arc of contact'of each roll with the work at any instant is lessened and, secondly the rolls frist engage the work in each cycle with a smaller impact. Both the rolling coiling the red at high speeds may be dispensed with.

Alternatively, the finishing stand speed may be maintained at a high value, and the cross-sectional area of the ingoing billet doubled so that the final coil weight is doubled over conventional practice.

Because of-the low amplitude of movement of the axes of the rol'ls'24, 25 resulting from the eccentric mounting frames, entry and-stripping guides can be fitted to the stand without interference with the moving I roll chocks.

' twist guides 54, in the caseof multi-stand operation,

load applied to the stand and the hammering to which the stand is subject are thus reduced.

The angle the major axis of each elliptical path makes withuthe pass line is preferably 20.

I claim: f

l. A rod orbar mill stand for giving a primary reduction to a workpiece, comprising a housing, a pair of mountings swingingly supported by the housing on opposite sides of the pass-line, a work roll carried by each mounting and designed to effect a first reduction of the workpiece to a rod or bar, means for driving the mountings in a synchronous movement in which the work roll axes are constrained to move in closed paths which, over a limited part, approach the pass-line so that, in use, the rolls intermittently and simultaneously engage the workpiece on opposite sides; and means for driving each work roll about its axis to give a peripheral speed differing from the peripheral speed of the roll surfaces due to the driving means for the mounting, such that the workpiece is urged by the work rolls in the feed direction.

2. A mill stand according to claim 1, in which the mountings are such that the work roll axes are constrained to paths which approach ellipses.

3. A mill stand according to claim 2, in which the major axes of the ellipses are inclined to the pass-line.

4. A mill stand according to claim 3, in which the major axes of the ellipses are inclined at angles of about to the pass-line.

5. A mill stand according to claim 2, in which the means for driving the mountings are such that the roll axes, when moving in the parts of the path closer to the pass-line, move in the direction opposite to the feed direction of the workpiece, and the means for driving the rolls about their axes are arranged to rotate the rolls at peripheral speeds in excess of the peripheral speeds of the roll surfaces due to the driving means for the mountings.

6. A mill stand according to claim 5, in which each mounting is a compound pendulum.

7. A mill stand according to claim 6, in which each mounting comprises a frame mounted on an eccentric drive shaft, and constrained at a point on the side of the drive shaft distant from the work roll to a substantially linear path.

8. A mill stand according to claim 7, in which each frame is constrained by a link or links pivoted to the frame and to the housing.

9. A 'mill stand according to claim 1, in which the means for driving the mountings comprise a gear box having an input shaft and output shafts connected to give equal and opposite movements to the mountings, and the means for driving the rolls about their axes comprise gearing operatively connected to the work rolls and to the input shaft to give a desired ratio between the speeds of rotation of the work rolls about their axes and the speeds at which the mountings are driven. I

10. A mill stand according to claim 1, in which each work roll has a plurality of aligned grooves for multistand rolling.

11. A continuous rod mil bar mil comprising a train of stands, of which at least the first stand is as claimed in claim 1.

12. A method of continuous rod or bar rolling comprising passing a workpiece through a train of rod or bar mill stands, causing the axes of each work roll of at least the first stand of the train to follow a closed path so that the work rolls contact and reduce the workpiece over a part only of the paths, the roll axes moving during such time as they contact the workpiece in a direction generally opposite to the direction of movement of the workpiece through. the stand, and driving the work rolls of that stand about their axes to give a peripheral speed in excess of the peripheral speed of the roll surfaces due to the movement of the roll axes, and in a direction to cause the workpiece to be urged in the feed direction.

13. A method according to claim 12 in which the mean linear speed of the workpiece at the first stand is less than 0.08 m/sec.

14. A method according to claim 12, in which the closed paths approximate to ellipses.

15. A method according to claim 14 in which the major axes of the ellipses are inclined to the pass-line.

16. A method according to claim 12, in which a common drive means drives firstly the rolls about their axes and secondly the roll axes along the closed paths through gearing which gives a required ratio between the angular velocities.

17. A method according to claim 12, in which a plurality of strands are simultaneously rolled by the train. l 

1. A rod or bar mill stand for giving a primary reduction to a workpiece, comprising a housing, a pair of mountings swingingly supported by the housing on opposite sides of the pass-line, a work roll carried by each mounting and designed to effect a first reduction of the workpiece to a rod or bar, means for driving the mountings in a synchronous movement in which the work roll axes are constrained to move in closed paths which, over a limited part, approach the pass-line so that, in use, the rolls intermittently and simultaneously engage the workpiece on opposite sides; and means for driving each work roll about its axis to give a peripheral speed differing from the peripheral speed of the roll surfaces due to the driving means for the mounting, such that the workpiece is urged by the work rolls in the feed direction.
 2. A mill stand according to claim 1, in which the mountings are such that the work roll axes are constrained to paths which approach ellipses.
 3. A mill stand according to claim 2, in which the major axes of the ellipses are inclined to the pass-line.
 4. A mill stand according to claim 3, in which the major axes of the ellipses are inclined at angles of about 20*to the pass-line.
 5. A mill stand according to claim 2, in which the means for driving the mountings are such that the roll axes, when moving in the parts of the path closer to the pass-line, move in the direction opposite to the feed direction of the workpiece, and the means for driving the rolls about their axes are arranged to rotate the rolls at peripheral speeds in excess of the peripheral speeds of the roll surfaces due to the driving means for the mountings.
 6. A mill stand according to claim 5, in which each mounting is a compound pendulum.
 7. A mill stand according to claim 6, in which each mounting comprises a frame mounted on an eccentric drive shaft, and constrained at a point on the side of the drive shaft distant from the work roll to a substantially linear path.
 8. A mill stand according to claim 7, in which each frame is constrained by a link or links pivoted to the frame and to the housing.
 9. A mill stand according to claim 1, in which the means for driving the mountings comprise a gear box having an input shaft and output shafts connected to give equal and opposite movements to the mountings, and the means for driving the rolls about their axes comprise gearing operatively connected to the work rolls and to the input shaft to give a desired ratio between the speeds of rotation of the work rolls about their axes and the speeds at which the mountings are driven.
 10. A mill stand according to claim 1, in which each wOrk roll has a plurality of aligned grooves for multi-stand rolling.
 11. A continuous rod mil bar mil comprising a train of stands, of which at least the first stand is as claimed in claim
 1. 12. A method of continuous rod or bar rolling comprising passing a workpiece through a train of rod or bar mill stands, causing the axes of each work roll of at least the first stand of the train to follow a closed path so that the work rolls contact and reduce the workpiece over a part only of the paths, the roll axes moving during such time as they contact the workpiece in a direction generally opposite to the direction of movement of the workpiece through the stand, and driving the work rolls of that stand about their axes to give a peripheral speed in excess of the peripheral speed of the roll surfaces due to the movement of the roll axes, and in a direction to cause the workpiece to be urged in the feed direction.
 13. A method according to claim 12 in which the mean linear speed of the workpiece at the first stand is less than 0.08 m/sec.
 14. A method according to claim 12, in which the closed paths approximate to ellipses.
 15. A method according to claim 14 in which the major axes of the ellipses are inclined to the pass-line.
 16. A method according to claim 12, in which a common drive means drives firstly the rolls about their axes and secondly the roll axes along the closed paths through gearing which gives a required ratio between the angular velocities.
 17. A method according to claim 12, in which a plurality of strands are simultaneously rolled by the train. 